An optical waveguide is, for example, a special optical part that performs the multiplexing, branching, switching and the like of light by producing a portion having a slightly higher refractive index than that of surroundings on or directly below the surface of a substrate to confine light. Specific examples of the optical waveguide include optical multiplexing/branching circuits, frequency filters, optical switches, and optical interconnection parts useful in the fields of communication and optical information processing. For example, a WDM (Wavelength Division Multiplexing) system that transmits time-shared signals at different wavelengths is a promising system capable of realizing high-speed, large-capacity communication needed in an altitude information-oriented society. Key optical devices in the WDM system are, for example, a light source, an optical amplifier, an optical multiplexing/branching device, an optical switch, a tunable filter, and a wavelength converter.
An optical waveguide device has, for example, the advantages that the device can realize sophisticated functions in a compact space on the basis of a precisely designed waveguide circuit as compared to an optical fiber part, can be put into volume production, and can integrate many kinds of optical waveguides in one chip.
Inorganic glass excellent in transparency and having small optical anisotropy has been heretofore mainly used as a material for an optical waveguide. However, the inorganic glass involves, for example, the problems that the glass is heavy, is apt to break, and requires a high production cost. Recently, there has been an active move toward the production of an optical waveguide part with a polymer material showing transparency in a visible light region below, for example, 0.85 μm or, at communication wavelengths in the range of, for example, 1.3 to 1.55 μm corresponding to an infrared region instead of the inorganic glass.
For example, Patent Document 1 discloses a curable composition for an optical material characterized in that the curable composition contains a silicon containing polymer having an epoxy group, a silicon atom having at least three oxygen atoms bonded to itself, a Si—R group (where R represents an alkyl group, phenyl group, alkylphenyl group or phenylyalkyl group, or an alkyl group, phenyl group, alkylphenyl group or phenylyalkyl group in which part or all of the hydrogen atoms in the R group are substituted with halogen or deuterium atom) and no Si—OH group and having a weight average molecular weight of from 500 to 1,000,000, and a curing catalyst as essential components; and a optical waveguide obtained by curing the curable composition.    Patent Document 1: JP-A-2004-10849, Claims